This invention relates to a holding mechanism for holding a workpiece while an operation is performed on it by an operating device which passes along the workpiece. The operation may be a passive one in which the operating device, in passing along the workpiece, scans the surface of the workpiece to determine the condition of the surface or, alternatively, the operating device may perform an active operation on the workpiece to modify its surface characteristics. An example of the former is an image scanner, where the image to be scanned, is placed on a cylinder which is then rotated about its axis while a scanning head moves axially along the cylinder. A scan of the image is obtained and this is recorded as the scanning head passes along the cylinder. An example of the second case is a center lathe where a workpiece is turned between center by a turning tool moving from one end of the workpiece to the other skimming the outside surface of the workpiece during its pass from one end to the other.
In cases such as these, once the operation has been performed on the workpiece, the clamp or other holding mechanism holding the workpiece in position is released to allow the workpiece to be removed and be replaced by a subsequent workpiece so that the operation can be repeated on the subsequent workpiece.